Summary of Working Paper No. 120-1998

Simulation Study Work Package 4 “Design of the NSR Service Ships.

Part I: Model Tests in Ice with M-224.

Part II: Design of 40 000 and 25 000 dwt Ice Breaking Bulk /Container Carrier”

By Ann-Cristin Forsén, Jari Kivelä and Erkki Ranki, Kværner Masa-Yards Technology, Helsinki, Finland.

PART I:

Model tests with a double acting tanker (DAT) equipped with two Azipod propulsion units, were performed at the Kvaerner Masa-Yards Arctic research centre (MARC) in February - Mars 1998.

The model tests are a part of the INSROP programme “Simulation of Ship Navigation Along the NSR”

Tests were carried out to find out the icebreaking capability of the vessel and the capability to penetrate ridges by running astern. Design basis for the ship indicates following icebreaking requirements:

to be able to maintain a speed of 3 knots (1.5 m/s) in the maximum level ice of 8 months of an average year.

maintain continuous movement in ice ridges with thickness which covers 70% of the ridges.

maintain continuous movement in ice under compression in more than 50% of ice compression cases.

According to the tests the vessel will not fulfil the requirement of level ice breaking capability set by the design criteria.

The vessel is able to break 1.75 m thick level ice with a speed of 1.25 m/s (2.5 kn) when going astern. The required speed is 1.5 m/s (3 kn). The requirements can be fulfilled if the bollard pull astern can be increased 10% or with some improvement of the aft body shape which can decrease the ice resistance with about 10 %.

In ridges the DAT concept is up to expectations. Ridges with thicknesses of 15 - 20 m in full scale can be penetrated without ramming, just by turning the Azipods. When going ahead in a 15 m thick ridge several rammings were needed to penetrate the ridge.

The capability to break out of own channel is better when running ahead. When going astern the stem makes it difficult to turn out of the channel by having problems with breaking the opposite edge of the channel.

PART II:

Design drawings, technical specifications etc.